This invention is directed to a vibration tester for ball bearings and associated devices which permits rapid screening of the units by manufacturers or users. More specifically, the invention is especially useful in testing miniature ball bearings (defined, for the purpose of this invention, as those bearings having OD less than 40 mm, but not limited to this size range).
A basic device, known as an Anderometer is used for testing and classifying imperfections in ball and roller bearings and is disclosed in U.S. Pat. No. 2,468,648. In accordance with this device, the radial velocity of the outer ring of a bearing is measured, with the bearings' inner ring spun on a spindle. This device has been successfully employed for measuring and detecting flaws in large bearings, however, it is too insensitive to measure imperfections in miniature bearings.
U.S. Pat. No. 3,745,815 discloses a device similar to the above-discussed Anderometer which provides a device wherein a bearing is spun on a spndle and a pick off measures the radial motion of the outer race. This patent disclosure is primarily concerned with the processing of the signal once it leaves the pick off. The disclosed circuitry measures in a high frequency range in response to the presence of pulse trains in the signal and not the signal itself.
Still further, a device disclosed in U.S. Pat. No. 3,023,604 having an inventor in common with the inventorship of this invention discloses a device called a VANT (Vibration and Noise Tester). This device measures axial velocity but its major problem is that it is difficult to calibrate and resonance is detected in the frequency window within which measurements are taken. Thus, results are interferred with as a result of resonance.
U.S. Pat. Nos. 1,992,453, 2,364,229, 2,796,759, 3,095,730 and 3,332,277 are illustrative of other types of devices used for measuring bearings. However, as in the case with the above-specifically disclosed devices, all of these devices suffer in that they are not readily adaptable for use in testing miniature bearings due to lack of sensitivity and thus are primarily limited to the testing of large massive bearings.